The present invention relates to a modular building wall unit and a method for making such unit. Preferably, the present wall units are suitable as load supporting wall elements made of hard foam material and concrete.
Prior art wall elements are constructed in the form of sandwiches comprising three layers. One of these layers forming the outer surface of the element is made of cement bonded light weight structural materials which simultaneously may form a supporting surface for plaster or stucco work. In the alternative the outer layer is suitable for attachment thereto of wood paneling or the like. The intermediate layer of these prior art structural elements comprises either foamed or inserted insulating material. The third layer which is the inwardly facing layer usually comprises a panel of sheetrock or the like. The first mentioned outwardly facing layer usually comprises so called light weight concrete. Light weight concrete is known as a combination of porous mineral components bonded to each other by hydraulically effective bonding means, such as cement, whereby the structural components such as prefabricated concrete slabs or the like confine a certain proportion of hollow spaces. Slabs or plates of this so called light weight concrete have a weight ranging betwen about 0.8 to 1.4kg/dm.sup.3. By employing a steam hardening or curing process the weight of such light weight structural elements may still further be reduced to about 0.45kg/dm.sup.3.
The above mentioned intermediate layer of insulating material comprises, for example, foam materials of the polyurethane type which are covered up even before curing with the sheetrock panel, the outer surface of which provides a surface which may be painted or which is suitable for paper hanging.
A significant disadvantage of the prior art structural elements as described above is seen in that they are suitable only for insertion into a supporting frame structure because these elements of aerated concrete are practically not capable of taking up any practically useful statical loads.
The foregoing disadvantage has been recognized heretofore. Thus, German Patent Publication 2,145,978 discloses a sandwich type structural element which comprises an outer layer formed by a reinforced concrete slab or plate. The production of this type of element has the drawback that the reinforced concrete slab must be dry in order to provide the necessary bonding with the subsequently applied intermediate layer of foam material, such as polyurethane foam.